Learning JS: Should I start with ES6 or ES5?

I am a PHP developer and also have some basic knowledge of JavaScript. Now I decided to learn JS inside out. I want to understand the language better and also write good code for frontend as well as backend (NodeJS).

One of the first things I encountered was the new rise of ES6. Up to now ES6 is not fully supported in all browsers so the need of Babel is still active. However I wonder if it is better to start learning ES5 and then ES6 to understand the evolution of JS or should I start with ES6 and don't waste time learning ES5 because it is going to fade in the future.